For the IdM side of things, there is SCIM:
It started as Simple Cloud Identity Management, but once it got to IETF, it was changed to "System for Cross-domain Identity Management". This initiative has been backed by Google, Ping Identity, Salesforce, Cisco, SailPoint, UnboundID, and others. You can see some of these names on one of the RFCs:
http://tools.ietf.org/html/draft-ietf-scim-core-schema-00
This API is just for identity management, and it has taken years to get to this point. I think it would take many more to get to a common API for everything else.